One example of power supply systems capable of feeding electric power from a single power adaptor to a plurality of load devices is an electric shaver with a cleaning device. FIGS. 21A and 21B show configurations of a power supply system for use in the electric shaver. As shown in FIG. 21A, an electric shaver 2 can be connected to a power adapter 1 which is formed of a RCC (ringing choke converter) and the like. As illustrated in FIG. 21B, a cleaning device 3 can also be connected to the power adapter 1. As depicted in FIG. 21B, it is possible not only to cleanse a blade of the electric shaver 2 but also to electrically charge the electric shaver 2 under the state that the electric shaver 2 is mounted on the cleaning device 3.
In this case, since the power adapter 1 is outputting a direct current of, e.g., 12V, the task of feeding electric power to a cleaning device driving circuit 4 in the cleaning device 3 and the task of charging the electric shaver 2 mounted on the cleaning device 3 are performed through branch lines just in that condition. However, the power adapter 1 needs to be connected to the cleaning device 3 or the electric shaver 2 by way of a contacting type contact point 5. Furthermore, due to the fact that the power adapter 1 is feeding electric power of a voltage as high as 12V to match the cleaning device 3 of high power consumption, the electric shaver 2 requires the use of a step-down power converter 7 for dropping the voltage to a level suitable for charging a secondary battery 6. Thus, the electric shaver 2 grows in size.
In the meantime, demand has existed for non-contact or contactless power feeding in an electric shaver which is frequently used in a water-abundant environment, e.g., in a lavatory. FIG. 22 illustrates a conventional power supply system by which power feeding is conducted in a contactless manner. A commercial alternating current inputted to a power adapter 12 through a power cord 11 is converted to a direct current in a converter 13. The direct current is converted to a high frequency alternating current in a voltage-resonant inverter 14 and then outputted from a primary coil 15 which is an output port of the power adapter 12.
The primary coil 15 is magnetically coupled in a detachable manner to a secondary coil 17 which is an input port of an electric shaver 16. The alternating voltage developed in the secondary coil 17 is converted to a direct voltage in a converter circuit 18 and then fed to a load 19 which is formed of a secondary battery and an electric motor. The converter circuit 18 is an A/D converter whose size is smaller than that of a DC-DC converter of the step-down power converter 7 noted above.
Accordingly, the configurations depicted in FIGS. 23A and 23B are provided if the contactless power supply system illustrated in FIG. 22 is applied to the power supply system shown in FIGS. 21A and 21B, to which a plurality of load devices including the cleaning device 3 is connectable.
A power adapter 21, which is formed of a voltage-resonant inverter and so forth, serves to output an alternating current of, e.g., 50 kHz and 30V, to a power transmission coil 24. A power receiving coil 25 of an electric shaver 22 can be connected in a contactless manner to the power transmission coil 24 as shown in FIG. 23A. Likewise, a power receiving coil 26 of a cleaning device 23 can be connected in a contactless manner to the power transmission coil 24 as shown in FIG. 23B.
As can be seen in FIG. 23B, an A/D converter 27 is provided in the cleaning device 23. The A/D converter 27 is adapted to generate, e.g., a direct current of 12V, and feed the same to a cleaning device driving circuit 28. In order to charge the electric shaver 22 kept mounted on the cleaning device 23, an inverter 29 formed of a voltage-resonant inverter and the like for outputting an alternating current of, e.g., 50 kHz and 30V, and a power transmission coil 30 are provided in the cleaning device 23.
In this regard, one example of parallel power feeding techniques using electromagnetic induction is disclosed in, e.g., Japanese Laid-open Application H3-101110A. The prior art reference is directed to an electromagnetic outlet socket device in which a plurality of primary coils serving as a socket body are embedded into a wall in parallel and a load-connected secondary coil serving as a socket cap is fitted into the socket body, thereby making it possible to simultaneously feed electric power to a plurality of loads in parallel and in a contactless fashion. Therefore, the prior art reference teaches nothing but a structure of electromagnetic coupling parts.
In the configurations shown in FIGS. 23A and 23B, the converter 27 and the inverter 29 need to be additionally provided in the cleaning device 23 for the purpose of realizing a contactless power feeding operation. This leads to an increase in size and costs.